Ear and Hearing

The Outer Ear

Sound energy spreads out from its sources. For a point source of sound, it spreads out according to the inverse square law. For a given sound intensity, a larger ear captures more of the wave and hence more sound energy.

The outer ear structures act as part of the ear's preamplifier to enhance the sensitivity of hearing.

The auditory canal acts as a closed tube resonator, enhancing sounds in the range 2-5 kiloHertz.

The Tympanic Membrane

The tympanic membrane or "eardrum" receives vibrations traveling up the auditory canal and transfers them
through the tiny ossicles
to the oval window, the port into the inner ear.

The
eardrum is some fifteen times larger than the oval window of the inner ear, giving an amplification of about
fifteen compared to a case where the sound pressure interacted with the
oval window alone.

The tympanic membrane is very thin, about 0.1 mm, but it is resilient and strong.(Zemlin) It is made up of three layers: the outer layer of skin, a layer of fibrous connective tissue, and a layer of mucous membrane.(Clark & Martin)

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You may reach information about the nearby structures of the ear by clicking on the item of interest on the illustration.